The present disclosure is directed generally to an aerosol particulate capture mechanism, and more particularly to an aerosol particulate capture mechanism that permits the flow of gas through the collection substrate.
Aerosol particle capture mechanisms are generally described by the physical interaction of a particle with a collection surface. Examples of some interactions are diffusion, interception, impaction, inertial impaction, gravitation settling, and electrostatic attraction among others. These interactions are dependent on the size, shape, and charge of the particles sampled and the physical characteristics of the respective collection surface. Some aerosol samplers sort particulate matter by aerodynamic diameters of a certain size while others attempt to capture as much material as possible regardless of particle size.
Previously, filtration devices employing the use of a surface filter can effectively filter aerosolized particles from sampled air, but particles are collected on a large surface decreasing the effective surface concentration and increasing particle bounce while generating a high pressure drop across the filtration media. To prevent particle bounce, some filters have an integrated electret filter which can reduce the need for high face velocities and prevent destruction of viable microorganisms by impaction while retaining by electrostatic charge effects. In addition, filtration devices have historically had inherently high pressure drops across the collection membranes, particularly for filters that have porosity and depth. Often times a high vacuum sampling pump is required to utilize fiber depth filters.
As mentioned, one of the main deficiencies of many types of aerosol samplers is particle bounce. This deficiency can result in reduced particle collection efficiencies; particularly for particles that exhibit repulsive verses attractive forces with the collection surface. One method to overcome this force is to accelerate the particles at a high velocity and drive them into a tacky/oily surface or to impact or entrap them into a liquid impinger. These methods are not conducive to in-situ analysis during collection, require post-sample collection clean up and processing, and generally do not concentrate all the particles sampled in a small surface area. Instead, the particles are eluted from the filter, causing dilution, and require manual concentration following collection.
In addition, impaction wells are often designed to comply with dimensions that favor collection of particles of a certain size. All impactors currently in the art have solid support under the collection material. This means there is no air flow through the collection media and its depth and filamented fibers are the primary entrapment mechanism. In addition, many depth filters such as, but not limited to, borosilicate glass, quartz, other forms of silicon dioxide, ceramic, metallic, and polymer based filters have naturally occurring electrets as opposed to induced electrets to help with particle retention.
Accordingly, there is a need in the art for an aerosol sampling device that can sample particulates while minimizing bounce and that does not rely solely on the depth of collection media, liquid entrapment, electrolytic effects, or methods requiring high vacuum to retain particulates.